Preloaded shock absorbing bushing and cam follower

ABSTRACT

A flexible bushing for a cam follower, comprising a substantially rigid inner sleeve including an inner cam follower engaging surface, a length of the inner sleeve being greater than a thickness of a ram into which the flexible bushing is inserted, a substantially rigid outer sleeve including an outer ram engaging surface, a length of the outer sleeve being substantially equal to the thickness of the ram, the inner and outer sleeves being substantially concentric, and a shock absorbing flexible material disposed between the inner and outer sleeves.

BACKGROUND INFORMATION

Prior apparatus for reshaping cylindrical metal containers (e.g., cans)have included can supporting devices including, for example, spindlehousings supporting spindle ram assemblies at intervals around theperiphery of a cylindrical ram block portion of a turret. The spindleram assemblies carry can reshaping tools which are rotatable about thespindle axes and which may be reciprocated along lines substantiallyparallel to the turret axis. The ram block is driven about the turretaxis thereby causing the spindle ram assemblies to orbit the turretaxis. When operating at high speeds, the cam followers of these devicesare often brought into and out of contact with a cam causing anincreased rate of wear and a higher incidence of failure for the camfollowers. Specifically, in the common instance where a cam follower isovergreased, the rotational speed of the cam followers decreasessignificantly when they lose contact with the cam. Then when the camfollowers come back into contact with the cam, the cam followers aresuddenly accelerated and skidding occurs between the cam and the camfollowers. This skidding is a significant source of cam follower wearand failure.

SUMMARY OF THE INVENTION

A flexible bushing for a cam follower, comprising a substantially rigidinner sleeve including an inner cam follower engaging surface, a lengthof the inner sleeve being greater than a thickness of a ram into whichthe flexible bushing is inserted, a substantially rigid outer sleeveincluding an outer ram engaging surface, a length of the outer sleevebeing substantially equal to the thickness of the ram, the inner andouter sleeves being substantially concentric, and a shock absorbingflexible material disposed between the inner and outer sleeves.

In addition, a cam follower assembly, comprising a cam followerextending through an opening in a ram, the cam follower including aracer to follow a contour of a cam, wherein, when the cam exerts adeflection force on the racer, a flexible material is deformed to absorbthe deflection force. Furthermore, a cam assembly, comprising a cam, afirst cam follower inserted through a ram, the first cam followerincluding a first racer contacting the cam, and a second cam followerinserted through a flexible bushing in the ram, the second cam followerincluding a second racer contacting the cam, wherein, as the first andsecond cam followers move relative to the cam, the cam exerts adeflection force deflecting the second cam follower deforming theflexible bushing.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a front elevation view of an exemplary embodiment of a canprocessing machine according to the present invention;

FIG. 2 shows a cross-sectional view of an exemplary cam followerassembly for a ram according to the present invention;

FIG. 3 shows a cross-sectional view of an exemplary bushing for the camfollower assembly according to the present invention;

FIG. 4 shows a cross-sectional view of an exemplary cam followerassembly for a ram in a deflected position according to the presentinvention;

FIG. 5 shows a top view of an exemplary ram having a removable end withan exemplary flexible bushing according to the present invention;

FIG. 6 shows a side view of an exemplary ram having a removable endaccording to the present invention;

FIG. 7 shows a cross-sectional view of an exemplary cam follower in analternative exemplary embodiment of the present invention;

FIG. 8 shows a detail view of an exemplary cam follower according to thepresent invention;

FIG. 9 shows a top view of an alternative embodiment of a removable endwith an exemplary flexible bushing according to the present invention;

FIG. 10 shows a side view of an alternative embodiment of a removableend according to the present invention.

DETAILED DESCRIPTION

The present invention may be further understood with reference to thefollowing description of preferred exemplary embodiments and the relatedappended drawings, wherein like elements are provided with the samereference numerals. It should be understood that the present inventionmay be implemented on any cam/cam follower arrangement operating at highfrequency and the term cam/cam follower arrangement will be usedthroughout this description to generically refer to all such devices.

FIG. 1 shows an exemplary embodiment of a can processing machine 10. Aturret 12 is mounted on a turret shaft 14 such that the turret 12 mayrotate. Pairs of axially aligned ram assemblies 20 and 50 are mountedaround the outer circumference of turret 12. The number of pairs of ramassemblies may vary based on the size of the ram assemblies, the size ofthe turret 12, the specific tooling operation, etc. Each ram assembly 20and 50 includes a ram housing 22 and 52, respectively, which is fixed toturret 12 and a ram 24 and 54, respectively, which move axially withinthe corresponding ram housings 22 and 52.

A first end of the ram 24 includes cam followers 26 and 28 having racers30 and 32, respectively. Similarly, a first end of the ram 54 includescam followers 56 and 58 having racers 60 and 62, respectively. Cams 34and 64 are provided at opposite ends of machine 10. The cam 34 engagesracers 30 and 32 of and the cam 64 engages racers 60 and 62. Those ofskill in the art will understand that cams 34 and 64 remain stationarywhile turret 12 rotates. As the turret 12 rotates, the racers 30 and 32remain engaged with the surface of the cam 34 moving the cam followers26 and 28 reciprocally as dictated by the shape of the cam 34. This, inturn, causes the ram 24 to reciprocate between a retracted position andan extended position within the ram housing 22. The same action occursat the other end of machine 10 causing ram 54 to reciprocate in the samemanner within housing 52. A typical can machine 10 has 2400reciprocations per minute, but those skilled in the art will understandthat the reciprocations may be more or less frequent depending on theoperation.

This reciprocating movement may cause a shaping tool 66 at a second endof the ram 54 to contact a can 90 when the ram 54 is in the extendedposition, while a space extends between the can 90 and the shaping tool66 when the ram 54 is in the retracted position. Similarly, a shapingtool 36 at a second end of ram 24 may contact the can 90 when the ram 24is in the extended position, while the shaping tool 36 is moved out ofthe can 90 when the ram 24 is in the retracted position. Through thereciprocating movement, the shaping tools 36 and 66 may perform thedesired operations on the can 90 (e.g., necking). Those of skill in theart will understand that there are numerous types of shaping tools 36and 66 that may be used to shape a can or other workpiece and thatmultiple shaping tools or other types of assemblies may be attached tothe second end of the rams 24 and 54 to perform operations onworkpieces. The present invention is not limited to the type of canmachine 10 described with reference to FIG. 1. The exemplary can machine10 is only described to illustrate an example of a type of machine wherethe present invention may be used.

FIG. 2 shows an exemplary cam/cam follower arrangement 10 including apair of cam followers 26 and 28 contacting opposite sides of a cam 34.The following description is provided for the pair of cam followers 26and 28, but those of skill in the art will understand that the samearrangement may be used for the pair of cam followers 56 and 58. Inaddition, FIGS. 2 and 4 show a slight gap between the racers 30 and 32and the cam 34. However, as described below, the present inventionallows the racers 30 and 32 to maintain constant contact with the cam34. The gaps are only shown in the figures to distinguish between thedifferent elements illustrated in the figures. Each of the cam followers26 and 28 includes a racer 30 and 32, respectively, rotatably mountedthereto by a bearing 102 and 104, respectively. Each of the camfollowers 26 and 28 is received in a corresponding opening in a bushing106 and 108 which may, for example, be press fit into a correspondingopening in the ram 24. Each of the cam followers 26 and 28 extendsthrough a central opening defined by the corresponding bushing 106 and108 to extend from a side of the ram 24 opposite the cam 34. Each of thecam followers 26 and 28 may be maintained in a desired position withinthe corresponding bushing 106 and 108 by, for example, nuts 110 and 112and washers (not shown), respectively.

An exemplary embodiment of a shock absorbing bushing according to thepresent invention will be described with reference to the bushing 108.Those skilled in the art will understand that the bushing 106 may beformed of a single substantially rigid sleeve 124 or may simply be anopening machined through ram 24. A bushing 106 having a substantiallyrigid sleeve 124 is preferred when the ram 24 is made of a relativelysoft material. When the ram 24 is a hard material (e.g., steel), thebushing 106 may be formed by machining an opening in the ram 24.

FIG. 3 shows a detail of bushing 108 which may be formed of asubstantially rigid concentric inner sleeve 114 and a substantiallyrigid outer sleeve 116 separated by a layer of flexible material 118.For example, the inner sleeve 114 and outer sleeve 116 may be formed ofmetal such as steel 4041, while the flexible material 118 may be formed,for example, of rubber such as rubber of durometer hardness 75. Asdescribed more fully below, the flexible material 118 will serve toabsorb vibrations, provide a small degree of mobility to the camfollower 108 and allow for a preload on the cam follower 108. Thoseskilled in the art will understand that a wide variety of materials maybe substituted for the exemplary materials listed herein withoutdeparting from the scope of the present invention.

The thickness of the flexible material 118 may vary depending on theoperating specifics of particular designs. However, according to theexemplary embodiment, the flexible material 118 will preferably beformed of hard rubber between 2 and 3 mm, more preferably approximately2.5 mm. In addition, an axial length of the outer sleeve 116 willpreferably be substantially equal to a thickness of the ram 24 so thatthe ends of the outer sleeve 116 are flush with the surfaces of the ram24. The axial length of the flexible material 118 and the inner sleeve114 will preferably exceed that of the outer sleeve 116 so that theflexible material 118 and the inner sleeve 114 extend past one or bothends of the outer sleeve 116. For example, for an outer sleeve 116 ofapproximately 0.78 inches in length, the flexible material 118 and theinner sleeve 114 may be 0.86 inches in length extending approximately0.04 inches (1 mm) beyond both ends of the outer sleeve 116.

A groove 120 may extend around the entire circumference of the outersleeve 116. The centerline of the groove 120 may preferably extendaround the outer sleeve 116 at a point approximately midway between theends thereof. Thus, a set screw inserted into an opening 122 (FIG. 2)may engage the groove 120 to secure the bushing 108 in a desiredposition with respect to the ram 24. In this manner, the bushing 108 maybe precisely located within the ram 24 (e.g., outer sleeve 116substantially flush with the surfaces of the ram 24. Those of skill inthe art will understand that bushing 108 may be secured within the ram24 using other methods, for example, press fitting, mechanicalfasteners, chemical fasteners (e.g., epoxy), etc. In addition, thebushing 108 may be formed as an integral part of the ram 24 or aremovable portion of the ram 24 (described in greater detail below).

In mounting the cam follower 28 into the bushing 108 with the nut 112,the clamping force is developed on the inner sleeve 114 leaving gaps 130and 132 between the cam follower 28 and the surface of the ram 24. FIG.8 shows a detail view of the cam follower 28 showing the gaps 130 and132 which will be substantially the same size as the length that theinner sleeve 114 extends from the outer sleeve 116 which issubstantially flush with the surfaces of the ram 24. In the examplaryembodiment described above, this length was approximately 1 mm on bothends, meaning that gaps 130 and 132 will be approximately 1 mm. Theclearance should be between 5 and 10% of the diameter of the camfollower shaft, preferably at least one (1) mm. As will be described ingreater detail below, the cam follower 28 will deflect such that theaxis 128 will no longer be parallel with the axis 126 of the camfollower 26. When this deflection occurs, the gap 132 must be largeenough that the racer 32 does not come in contact with the surface ofthe ram 24. If the racer 32 were to contact the surface of the ram 24,it would prevent the racer 32 from rotating freely while it was incontact with the cam 34. Those of skill in the art will understand thata gap 134 will also extend between the racer 30 of the cam follower 26and the ram 24 such that racer 30 may freely rotate about axis 126.

In a first exemplary embodiment, when the cam 34 is inserted (in itsneutral or zero displacement section) and engages the racers 30 and 32of cam followers 26 and 28, respectively, the axes 126 (of cam follower26), 128 (of cam follower 28) and 136 (of cam 34) are substantiallyparallel (as shown in FIG. 2). This arrangement excludes a preload whichis described in greater detail below. As the turret 12 rotates and theracer 32 follows the contour of the cam 34, a high force is exerted bythe cam 34 against racer 32. This force is a high frequency force basedon the shape of the cam 34 and the speed of rotation of the turret 12.In response to this impact, cam follower 28 is deflected and theflexible material 118 of bushing 108 is slightly deformed to absorb anyshock due to the deflection force.

FIG. 4 shows shows a cross-sectional view of an exemplary cam follower28 in a deflected position. As described above, the cam follower 28follows the contour of the cam 34. During the working cycle (onerotation of turret 12), when the ram 24 is pulled away from the can 90,the cam 34 profile rises, presenting a sudden and steep incline in thepath of the cam follower 28. The force resulting from the rotationalimpact of the cam follower 28 on the incline (curvature) of the cam 34and the acceleration of the mass presented by the ram 24 causes the camfollower 28 to deflect. This deflection force is transmitted from thecam follower 28 to the inner sleeve 114 of the bushing 108 and throughto the flexible material 118 of the bushing 108. As shown in FIG. 4,this deflection force causes the flexible material 118 to be compressedin areas and expanded in other areas. This action of the flexiblematerial 118 absorbs the high frequency shock load exerted by the cam 34on the cam follower 28. However, as the cam follower 28 is deflected,the outer sleeve 116 of bushing 108 remains in the same positionrelative to the ram 24.

The deflection of the cam follower 28 is illustrated in FIG. 4 byshowing the original axis 128 before any deflection and the new axis 136after the deflection. The deflection is shown as angle 138 which may be,for example, three to five degrees (3°-5°) for an exemplary cam and camfollower. When this deflection occurs, the width of the gaps 130 and 132is decreased. However, as described above, the width of the gaps 130 and132 is selected so that the deflection does not completely eliminate thegaps 130 and 132 and the racer 32 may continue to freely rotate withoutcontacting the surface of the ram 24.

The racer 32 of the cam follower 28 is crowned such that, when in theneutral position, a maximum diameter portion of the crown contacts thecam 34 (i.e., the maximum contact area between the racer 32 and the cam34). When the cam follower 28 is deflected, the contact between theracer 32 and the cam 34 remains on the crown within a short distance ofthe center thereof and within a desired contact area surrounding thecenter of the crown. The crown is sized so that, at a time of maximumdeflection of the racer 32, the cam 34 contacts the crown so that wearon the racer 32 is reduced, thereby prolonging the life of the camfollower 28. In other words, the present invention maintains contactbetween the racer 32 and the cam 34 over a maximum contact area from theneutral position through the largest angle of deflection so that thereis no single point of wear on the racer 32.

As the turret 12 continues to rotate away from the incline back to theneutral position of the cam 34, the deflection force exerted on the camfollower 28 decreases and the flexible material 118 returns to itsoriginal shape. When the cam 34 reaches its neutral position, the camfollowers 26 and 28 and the cam 34 are returned to the parallel positionas shown in FIG. 2. As described above, the turret 12 may be rotated ata speed which deflects the cam follower 28 hundreds of times per minute.Thus, flexible material 118 may absorbs thousands of shock loads duringa period of continuous operation (e.g., a twenty-four period) whichcould cause excessive wear on the cam follower 28 and the cam 34.

In a second exemplary embodiment, a preload may be applied to the camfollower 28 in order to maintain the racers 30 and 32 in contact withthe cam 34. To obtain a preload, the cam followers 26 and 28 may bealigned so that, if cam 34 is not received therebetween, a distanceseparating the racers 30 and 32 of the corresponding cam followers 26and 28 is less than the width of the neutral position of the cam 34(e.g., the thinnest portion of the cam 34) to be received therebetween.For example, for a cam 34 having a neutral position thickness of 1.0045inches, the separation between the racers 30 and 32 may be 1.0035inches, resulting in a preload of 0.001 inches. Such a preload willresult in a deflection of less than one degree (<1°) of the cam follower28 when the cam 34 is inserted between the racers 30 and 32 (e.g. angle138 in FIG. 4 is less than 1° when the neutral position of the cam 34 isbetween the racers 30 and 32). Thus, when the cam 34 is received betweenthese racers 30 and 32, the racers 30 and 32 will be biased toward thesurface of the cam 34 maintaining the cam followers 26 and 28 in contactwith the cam 34 even when the cam 34 moves at high speed. Thus, therotational speed of the racers 30 and 32 remains substantially constantavoiding rapid acceleration and deceleration associated with loss ofcontact.

The operation of the cam follower 28 and the bushing 108 during therotation of the turret 12 is the same as described above for the firstembodiment. The cam follower 28 will be deflected by the force of thecam 34 as the turret 12 rotates and the flexible material 118 of thebushing 108 will absorb the shock caused by the deflection force of thecam 34. The maximum deflection of the cam follower 28 will be increasedby the amount of the preload on the cam follower 28 (e.g., 0.5°) and thecam follower 28 will return to its original position (i.e., the positionwhere the only deflection is caused by the preload) when the turret 12rotates the cam follower to the neutral position of the cam 34. Thus,the flexible bushing 108 allows for a preload and absorbs shock, both ofwhich contribute to extending the life of the cam follower 28 and thecam 34, as well as allowing the turret 12 to rotate faster, therebyincreasing the efficiency of the machine 10. The permanent contact ofthe cam followers 26 and 28 with the cam 34 and the constant racerrotation provided by the exemplary embodiment of the present inventionextends the life of the cam followers and cam. The flexible bushing 108is also designed so that it may be retrofitted onto existing rams.

As shown in FIGS. 1 and 2, the bushing 108 with the flexible material118 is for the cam followers 28 and 58 which are closest to the end ofthe rams 24 and 54, respectively. FIG. 5 shows a top view of a ram 24having a removable end 150 with a bushing 108. The ram 24 has a solidportion 152 having a bushing 106 for the insertion of a cam follower.The ram 24 also has a removable end 150 having a flexible bushing 108(including inner sleeve 114, outer sleeve 116 and flexible material118). The removable end 150 is connected to the solid portion 152 of theram 24 using the couplers 154 and 156. FIG. 6 shows a side view of theram 24 with the coupler 156 and the solid portion 152 having two vias158 and 160 to fasten the coupler 156 to the solid portion 152. Thefastening may be accomplished using, for example, two screws or bolts.The coupler 154 is similarly attached to the solid portion 152. FIG. 6additionally shows a via 162 which extends the full length of theremovable end 150 and into the coupler 156. Another screw maybe used tofasten the removable end 150 to the coupler 156, thus attaching theremovable end 150 to the solid portion 152 of the ram 24. Therefore, ifthe bushing 108 or the cam follower inserted through the bushing 108becomes worn so that a replacement is needed, the removable end 150 maybe removed by simply taking out two screws that attach the removable end150 to the couplers 154 and 156. When the bushing 108 or the camfollower has been repaired, the removable end 150 may be reattached tothe ram 24 using the two screws. In addition, a replacement removableend 150 may replace a removable end 150 with a worn bushing 108 or camfollower. The removable end 150 may also be removed for access to thecam. The removable end 150 allows for a fast and easy maintenance to amachine implementing exemplary embodiments of the present invention. Thelength (l) of the removable end 150 determines the amount of preload forthe cam followers (e.g., cam followers 26 and 28). The shorter thelength (l), the greater the amount of preload. The preload is achievedduring assembly by tightening the two screws.

FIGS. 9 and 10 show an alternative embodiment of the removable end 150.In this embodiment, the flexible material 118 is a part of the removableend 150, while the inner sleeve 114 may also be part of the removableend 150 or part of the cam follower (not shown), for example, the shankor neck of the cam follower. In this embodiment, the outer sleeve is notshown because the removable end 150 forms the outer sleeve to which theflexible material 118 is formed. When a cam follower is inserted throughthe removable end 150, the flexible material 118 operates in the samemanner as described above to absorb the deflective force on the camfollower.

FIG. 7 shows an alternative embodiment of a cam follower 200. The camfollower 200 has a racer 202 riding on a bearing 204 and may be securedto a ram using a nut 206. In the neck area of the cam follower 200, anentire circumference of the solid center core 208 is surrounded by aflexible material sleeve 210, which may be formed of the same materialas the flexible material 118 of the bushing 108 described above. Theflexible material sleeve 210 may be, for example, vulcanized to the neckor shank of the cam follower. The flexible material sleeve 210 issurrounded by a substantially rigid sleeve 212 having a groove 214. Theflexible material sleeve 210 provides substantially the same function asthe flexible material 118 of the bushing 108, while the substantiallyrigid sleeve 212 and the groove 214 provide substantially the samefunction as the outer sleeve 116 and the groove 120 of the bushing 108.When using the cam follower 200, it is not necessary to use a bushing108 including the flexible material 118 as described above. Rather, thecam follower 200 may be press fit directly into the ram and secured viaset screws that engage groove 214 of rigid sleeve 212 (e.g., two setscrews which oppose each other 180°). Those of skill in the art willunderstand that the nut 206 may be used for saftey so that in the eventthat the flexible material sleeve 210 wears out, the cam follower 200will be prevented from slipping through the ram into the machine.

The flexible material sleeve 210 and the rigid sleeve 212 should beformed on the shank so that when inserted into the ram, there are gapsbetween the ram and the racer 202, for example, gap 132 as shown in FIG.8. As a deflection force is exerted by a cam on the cam follower 200,the cam follower 200 will deflect off of the axis 212 in the same manneras described above for cam follower 28. However, instead of the flexiblematerial of the bushing absorbing the shock of the deflection force, theflexible material 210 of the cam follower 200 will absorb the shock bycompressing in areas and expanding in other areas. When the deflectionforce is decreased or taken away completely, the flexible material 210returns to its original shape with the cam follower 200 parallel to theaxis 216. The cam follower 200 may also be used to form a preload.

In the preceding specification, the present invention has been describedwith reference to specific exemplary embodiments thereof. It will,however, be evident that various modifications and changes may be madethereunto without departing from the broadest spirit and scope of thepresent invention as set forth in the claims that follow. Thespecification and drawings are accordingly to be regarded in anillustrative rather than restrictive sense.

What is claimed is:
 1. A cam follower assembly, comprising: a camfollower extending through an opening in a ram, the cam followerincluding a racer to follow a contour of a cam; and a flexibleelastomeric material inserted into the opening between the cam followerand the ram, wherein, when the cam exerts a deflection force on theracer, the flexible elastomeric material is deformed to absorb thedeflection force.
 2. The cam follower assembly of claim 1, furthercomprising a flexible bushing including the flexible material.
 3. Thecam follower assembly of claim 1, wherein the flexible material is aflexible sleeve portion of the cam follower.
 4. The cam followerassembly of claim 1, wherein, when the racer engages the cam in aneutral position, the cam follower is deflected forming a preload. 5.The cam follower assembly of claim 1, wherein the cam follower extendsthrough a removable end of the ram.
 6. The cam follower assembly ofclaim 5, wherein the flexible material is a flexible sleeve portion ofthe ram.
 7. The cam follower assembly of clam 5, wherein, when inoperation, the removable end of the ram remains in a fixed positionrelative to a fixed portion of the ram.
 8. A cam assembly, comprising: acam; a first cam follower inserted through a ram, the first cam followerincluding a first racer contacting the cam; and a second cam followerinserted through a flexible bushing including an elastomer in the ram,the second cam follower including a second racer contacting the cam,wherein, as the first and second cam followers move relative to the cam,the cam exerts a deflection force deflecting the second cam followerwhich deforms the elastomer of the flexible bushing to absorb thedeflection force.
 9. The cam assembly of claim 8, wherein a distancebetween the first racer and the second racer is less than a thickness ofthe cam in a neutral position, thereby forming a preload.
 10. The camassembly of claim 8, wherein the first cam follower is inserted througha fixed portion of the ram and the second cam follower is insertedthrough a removable end of the ram.
 11. The cam assembly of claim 10,wherein, when the cam assembly is operable, the removable end of the ramremains in a fixed position relative to the fixed portion of the ram.